In this research, we propose a novel recommendation for improving CCT-D and lumen output (LO) of the 6600K in-cup packaging white LEDs (ICP-WLEDs) by varying its particle concentration. By using Light Tools and Mat lab software based on the Mie Theory, we derive the influence of the red phosphor particle’s concentration on the D-CCT and LO. The results show that the CCT-D are significantly affected when the concentration of the red phosphor varying from 0% to 1.8%. The CCT-D decreases from 4000K to 2200K and LO increases from 800 lm to 1300 lm.
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As rare-earth-free alternatives, the manganese-based phosphors K2SiF6:Mn4+ has d-d transitions,
which are partially spin-allowed for Mn4+. Upon incorporation in the host compound, Mn4+ is the preferred
valence state for LED applications, due to better excitation properties and narrower emission bands. In
K2SiF6:Mn4+, the Intra configurational 3d3 transitions of the Mn4+ ion are responsible for the
luminescence, yielding narrow line emission. Furthermore, K2SiF6:Mn4+ has the relatively high values of
the color quality scale (CQS), color purity and absorption strength. The specific red line emission is seen in
K2SiF6:Mn4+ around 630 nm is caused by 3d3–3d3 transitions in Mn4+.The 3d3 electron configuration of
Mn4+ results in 120 possible distributions of the three electrons over the ten available single-particle states of
the 3d shell. The electronic Coulomb repulsion gives rise to a splitting of the 120-fold degenerate
configuration in eight LS terms that can be found for the free Mn4+ ion, the magnitude of this splitting is
characterized by the Racah parameters B and C [13-14]. This red phosphor can be considered as the
prospective candidate for improving color quality of the white LEDs.
In this research, the red-emitting K2SiF6:Mn4+ conversion phosphor is considered as a novel
recommendation for increasing the CCT-D and LO of the 6600K in-cup packaging white LEDs (ICP-
WLEDs). The effect of the red-emitting K2SiF6:Mn4+ conversion phosphor is investigated based on Mie
Theory with helping of the Mat Lab and Light Tools software. The research results show that the CCT
deviation (CCT-D), lumen output (LO) has been remarkably affected while the concentration of the red-
emitting K2SiF6:Mn4+ conversion phosphor’s particle varies. Finally, the red-emitting K2SiF6:Mn4+
conversion phosphor can be considered as a novel recommendation for WLEDs manufacturing. The main
contributions of this manuscript can be summarized as the followings:
a. The physical model and mathematical description of the ICP-WLEDs is conducted and formulated by
Mat Lab and Light Tools software based on Mie Theory.
b. The scattering process in the phosphor layer of the ICP-WLEDs is investigated.
c. The CCT-D and LO are analyzed and discussed in connection with varying the concentration of the red
phosphor particles.
2. RESEARCH METHOD
In this research, we use the real model of WLEDs as shown in Figure 1(a) for simulating the
physical model of ICP-WLEDs as shown in Figure 1(b). In this simulation model, we set the main
parameters of the 6600K CP-WLEDs as;
a. The depth, the inner and outer radius of the reflector to 2.07 mm, 8 mm and 9.85 mm, respectively.
b. LEDs chips are covered with a fixed thickness of 0.08 mm and 2.07 mm.
c. Each blue chip has a dimension of 1.14 mm by 0.15mm, the radiant flux of 1.16 W, and the peak
wavelength of 453 nm as shown in Figure 1(b) [11-13].
(a) (b)
Figure 1. (a) The WLEDs product of the Siliconware Precision Industries Co., Ltd.,Taiwan,
(b) ICP-WLEDs
For demonstrating the influence of the red phosphor’s concentration on the CCT-D and LO, we can simulate
the scattering and reduced scattering processes inside the phosphor layer of the 6600K ICP-WLEDs based on
the Mie-scattering [15-20]. The below expressions can compute the scattering coefficient μsca(λ) (mm-1),
and reduced scattering coefficient δsca(λ) (mm-1).
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Improving CCT-D and LO of the 6600K ICP-WLEDs by K2SiF6:Mn4+ phosphor (Phu Tran Tin)
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( ) ( ) ( , )
sca sca
N r C r dr
(1)
(1 )
sca sca g
(2)
In these equations, N(r) indicates the distribution density of diffusional particles (mm3
). Csca is the
scattering cross sections (mm2
), λ is the light wavelength (nm), r is the radius of diffusional particles (µm),.
Moreover, N(r) can be calculated by:
( ) ( ) ( ) .[ ( ) ( )]
dif phos N dif phos
N r N r N r K f r f r
(3)
N(r) is composed of the diffusive particle number density Ndif(r) and the phosphor particle number
density Nphos(r). In these equations, fdif(r) and fphos(r) are the size distribution function data of the diffusor and
phosphor particle. Here KN is the number of the unit diffusor for one diffuser concentration and can be
calculated by the following equation:
( )
N
c K M r dr
(4)
Where M(r) is the mass distribution of the unit diffuser and can be proposed by the below equation:
3
4
( ) [ ( ) ( )]
3
dif dif phos phos
M r r f r f r
(5)
Here ρdiff(r) and ρphos(r) are the density of diffuser and phosphor crystal.
3. RESULTS AND DISCUSSION
In this section, the influence of the red phosphor particles’ concentration on the scattering process
inner the phosphor layer of the 6600K ICP-WLEDs is investigated using Mat Lab software in the first stage.
After that, the CCT-D and LO of the 6600K ICP-WLEDs are analyzed and discussed in connection with
varying the concentration of the red phosphor from 0% to 1.8%. The scattering and reduced scattering
processes inner phosphor layer are drawn in Figure 2 and 3. Figure 2 indicates that the scattering coefficient
of 453 nm, 55nm, and 680 nm significantly increase while the concentration of the red phosphor varying
from 1% to 5 %. In addition, the coefficient of 555 nm has the highest increase in comparison with others.
On the same way, the reduced scattering coefficients of 453 nm, 55nm, and 680 nm have a considerable
increase while the concentration of the red phosphor varying from 1% to 5 %. All 453 nm, 55nm, and 680
nm reduced scattering coefficients increase in the same direction with each other as shown in Figure 3. From
that point of view, it is observed that the scattering process in the phosphor layer of the 6600K ICP-WLEDs
can be controlled by varying the concentration of the red phosphor.
Figure 2. Scattering coefficients Figure 3 Reduced scattering coefficient
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Moreover, the CCT-D and LO versus the red phosphor particles’ concentration are illustrated in
Figure 4 and 5. In this analysis, the concentration of the red phosphor is controlled from 0% to 1.8%. From
the research results, we can see that the CCT-D has a huge decrease and the LO has a massive increase with
increasing the concentration of the red phosphor. When the concentration of the red phosphor from 0% to
1.8%, CCT-D decreases from 4000K to 2200K and LO increase from 800lm to 1300 lm. It can be observed
that we can improve the CCT-D and LO of the 6600K ICP-WLEDs by controlling the concentration of the
red phosphor particles.
Figure 4. CCT-D versus Wt.% Figure 5. LO versus Wt. %
4. CONCLUSION
In this research, a novel recommendation for improving CCT-D and LO of the 6600K ICP-WLEDs
by varying its particle concentration is considered. By using Light Tools and Mat lab software based on the
Mie Theory, we derive the influence of the red phosphor particle’s concentration on the D-CCT and LO. The
results show that the CCT-D are significantly affected when the concentration of the red phosphor varying
from 0% to 1.8%. The CCT-D decreases from 4000K to 2200K and LO increases from 800 lm to 1300 lm.
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